U.S. Pat. No. 5,409,000 discloses an ablation catheter with an ultrasound transducer and an ablation electrode. Ultrasound waves are coupled into cardiac tissue and ultrasound echoes, which return from the cardiac tissue, are picked up by the ultrasound transducer and visualized on a screen. A physician performing an ablation procedure can observe the resulting ultrasound image on the screen, in order to perform the ablation procedure depending on the ultrasound image. The ablation procedure is performed by applying radio frequency (RF) current to an ablation electrode located at the tip of the ablation catheter.
A disadvantage of RF ablation together with ultrasound imaging inside the same catheter is the capacitive and/or conductive coupling of the RF signal onto the ultrasound signal generated by the ultrasound transducer and used for forming the ultrasound image. This reduces the quality of the ultrasound signal and, thus, of the ultrasound image used for monitoring the ablation procedure.